Seal assembly and an associated method thereof

ABSTRACT

A seal assembly, for example, a face seal assembly for a machine such as a turbomachine, and an associated method of operating the seal assembly in the machine are disclosed. The seal assembly includes a rotatable seal component, a non-rotatable seal component, and a plurality of pairs of flexures. The non-rotatable seal component is disposed facing the rotatable seal component. The plurality of pairs of flexures is spaced apart from each other along a circumferential direction of the seal assembly. Each pair of the plurality of pairs of flexures includes a first flexure and a second flexure disposed in a stressed condition such that a portion of the first flexure and a portion of the second flexure are in contact with each other. Further, an end of the first flexure and an end of the second flexure are coupled to each other and to the non-rotatable seal component.

BACKGROUND

Embodiments of the present specification relate generally to a sealassembly for a machine, and more particularly to a damped biasing memberfor the seal assembly and an associated method thereof.

In a seal assembly, for example, a face seal assembly, a stator sealcomponent is coupled to a stator via a driving member. The stator sealcomponent is moved along an axial direction of the face seal assembly bya plurality of biasing members such as helical springs disposed in thedriving member. During operation, the stator seal component maintains aclearance from a rotor seal component of the face seal assembly.Generally, the stator seal component includes a tongue and the drivingmember has a groove to enable the tongue to slide along the groove formoving the stator seal component along the axial direction. The groovemay be clogged with dust particles during a period of use, therebyobstructing/limiting the axial movement of the stator seal component.The use of helical springs may further limit a span of the axialmovement of the stator seal component. Further, the helical springs mayeither respond excessively or moderately to vibrations, thereby failingto efficiently attenuate vibrations, resulting in quick wear of thestator and/or rotor seal components.

BRIEF DESCRIPTION

In accordance with aspects of the present specification, a seal assemblyis disclosed. The seal assembly includes a rotatable seal component, anon-rotatable seal component, and a plurality of pairs of flexures. Thenon-rotatable seal component is disposed facing the rotatable sealcomponent. The plurality of pairs of flexures is spaced apart from eachother along a circumferential direction of the seal assembly. Each pairof the plurality of pairs of flexures includes a first flexure and asecond flexure disposed in a stressed condition such that a portion ofthe first flexure and a portion of the second flexure are in contactwith each other. Further, an end of the first flexure and an end of thesecond flexure are coupled to each other and to the non-rotatable sealcomponent.

In accordance with another aspect of the present specification, amachine is disclosed. The machine includes a stator housing, a rotor,and a seal assembly such as a face seal assembly. The rotor is disposedin the stator housing. The seal assembly is disposed between the statorhousing and the rotor. The seal assembly includes a rotatable sealcomponent, a non-rotatable seal component, and a plurality of pairs offlexures. The rotatable seal component is coupled to the rotor. Thenon-rotatable seal component is disposed facing the rotatable sealcomponent. The plurality of pairs of flexures is disposed spaced apartfrom each other along a circumferential direction of the seal assembly.Each pair of the plurality of pairs of flexures includes a first flexureand a second flexure disposed in a stressed condition such that aportion of the first flexure and a portion of the second flexure are incontact with each other. Further, a first end of the first flexure and afirst end of the second flexure are coupled to each other and to thenon-rotatable seal component. Similarly, a second end of the firstflexure and a second end of the second flexure are coupled to each otherand to the stator housing.

In accordance with yet another aspect of the present specification, amethod of operating a seal assembly is disclosed. The method involvesdriving a rotatable seal component coupled to a rotor disposed inside astator housing. The method further involves injecting a pressurizedfluid via a non-rotatable seal component against the rotatable sealcomponent and forming a layer of the pressurized fluid and a processfluid in a clearance defined between the rotatable seal component andthe non-rotatable seal component. Further, the method involvesregulating a flow of a portion of the process fluid through theclearance. Moreover, the method involves moving the non-rotatable sealcomponent along an axial direction relative to the rotatable sealcomponent, using a plurality of pairs of flexures. Each pair of theplurality of pairs of flexures includes a first flexure and a secondflexure disposed in a stressed condition such that a portion of thefirst flexure and a portion of the second flexure are in contact witheach other. Further, a first end of the first flexure and a first end ofthe second flexure are coupled to each other and to the non-rotatableseal component, and a second end of the first flexure and a second endof the second flexure are coupled to each other and to the statorhousing. Further, the method involves adjusting movement of thenon-rotatable seal component, using the plurality of pairs of flexures,and the layer of the pressurized fluid and the process fluid to maintainthe clearance between the non-rotatable seal component and the rotatableseal component. The method further involves damping vibrations of thenon-rotatable seal component and the stator housing by biasing the firstflexure and the second flexure against each other.

DRAWINGS

These and other features and aspects of embodiments of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a partial perspective view of a portion of a machine includinga stator, a rotor, and a seal assembly, in accordance with aspects ofthe present specification;

FIG. 2 is a perspective view of a portion of a rotor of FIG. 1, inaccordance with aspects of the present specification;

FIG. 3 is top view of a portion of a seal assembly of FIG. 1 including afirst flexure and a second flexure of a plurality of pairs of flexures,in accordance with aspects of the present specification;

FIG. 4 is a side view of a third flexure of a plurality of thirdflexures, in accordance with aspects of the present specification;

FIG. 5 is a top view of a portion of a seal assembly, in accordance withaspects of the present specification;

FIG. 6 is a top view of a portion of a seal assembly, in accordance withaspects of the present specification;

FIG. 7 is a top view of a portion of a seal assembly, in accordance withaspects of the present specification;

FIG. 8 is a top view of a portion of a seal assembly, in accordance withaspects of the present specification; and

FIG. 9 is a flow chart illustrating a method of operating a sealassembly, in accordance with aspects of the present specification.

DETAILED DESCRIPTION

Embodiments discussed herein disclose a seal assembly, for example, aface seal assembly for a machine such as a turbomachine. In someembodiments, the turbomachine may include, but not limited to, a gasturbine, a steam turbine, a supercritical carbon dioxide turbine, aturbo compressor, a hydro turbine, and the like. The seal assemblyincludes a rotatable seal component, a non-rotatable seal component, anda plurality of pairs of flexures. In some embodiments, the rotatableseal component and the non-rotatable seal component may be collectivelyreferred to as a “primary seal.” The plurality of pairs of flexures isdisposed spaced apart from each other along a circumferential directionof the seal assembly. Each pair of the plurality of pairs of flexuresincludes a first flexure and a second flexure disposed in a stressedcondition such that a portion of the first flexure and a portion of thesecond flexure are in contact with each other. It should be noted hereinthat the term “stressed condition” refers to a bent condition of thefirst and second flexures along mutually opposite directions. Forexample, the first flexure is bent inwardly and the second flexure isbent outwardly such that a portion of the first flexure and a portion ofthe second flexure are in contact with each other. Further, an end ofthe first flexure and an end of the second flexure are coupled to eachother and to the non-rotatable seal component. In certain embodiments,the plurality of pairs of flexures are configured to move thenon-rotatable seal component along an axial direction of the sealassembly and damp vibrations by biasing the first and second flexuresagainst each other.

In one embodiment, a seal assembly is disposed between a stator housingand a rotor of a machine such as a turbomachine. The rotatable sealcomponent is coupled to the rotor. A first end of the first flexure anda first end of the second flexure are coupled to each other and to thenon-rotatable seal component. A second end of the first flexure and asecond end of the second flexure are coupled to each other and to thestator housing. The non-rotatable seal component is disposed facing therotatable seal component to define a clearance (i.e., a first clearance)therebetween. Also, the non-rotatable seal component further includes arecess for holding a secondary seal. The non-rotatable seal component isdisposed facing the stator housing to define a second clearance therebetween.

In certain embodiments, the seal assembly further includes a pluralityof third flexures. In such embodiments, at least one third flexure ofthe plurality of third flexures is disposed between the first and secondflexures. Further, the seal assembly may include a plurality of firstwedge washers, a plurality of second wedge washers, and a plurality offasteners. In such embodiments, the plurality of first wedge washers isdisposed between the first flexure and the at least one third flexure.The plurality of second wedge washers is disposed between the secondflexure and the at least one third flexure. The first flexure and thesecond flexure are coupled to each other via the plurality of fastenersextending through the plurality of first and second wedge washers andthe at least one third flexure.

During operation, the first and second flexures are configured to adjustmovement of the non-rotatable seal component to maintain the firstclearance between the non-rotatable seal component the rotatable sealcomponent. Further, the first and second flexures are configured to dampthe vibrations of the non-rotatable seal component and the statorhousing. In some other embodiments, at least one third flexure of theplurality of third flexures is configured to further damp the vibrationsof the non-rotatable seal component and the stator housing. In oneembodiment, at least one flexure of the first flexure, the secondflexure, and the at least one third flexure is a leaf spring. In anotherembodiment, one flexure of the plurality of third flexures is at leastone of a bellow spring, a W-shaped spring, and a V-shaped spring. In oneembodiment, at least one flexure of the plurality of first flexures, theplurality of second flexures, and the at least one third flexureincludes a truss-like structure to regulate an axial stiffness of thedamped biasing members. A portion of each of the first flexure, thesecond flexure, and the at least one third flexure rub against eachother resulting in dissipation of heat from the non-rotatable sealcomponent. In some embodiments, the portion of each of the firstflexure, the second flexure, and the at least one third flexure isprovided with a wear resistant coating.

FIG. 1 illustrates a partial perspective view of a portion of a machine10, in accordance with aspects of the present specification. The machine10 includes a rotor 12, a stator housing 14, and a seal assembly 16 suchas a face seal assembly disposed between the stator housing 14 and therotor 12. In certain embodiments, the seal assembly 16 is used tocontrol leakage of a process fluid 17 between regions “P₁,” “P₃” ofrelatively high pressure to regions “P₂,” “P₄” of relatively lowpressure. In the illustrated embodiment, the machine 10 is a gas turbineengine and the seal assembly 16 is a compressor discharge pressure sealassembly disposed between the rotor 12 and the stator housing 14. Therotor 12 is a core shaft and the stator housing 14 is a diffuser casing.Although the gas turbine engine 10 is illustrated, the seal assembly 16may be used in other applications where a self-adjusting seal isrequired. In some embodiments, the machine 10 may be a centrifugalcompressor, a steam turbine, a gas turbine, an electric generator, andthe like. It may also be noted that the aspects of the presentspecification are not limited to rotary machines and may be associatedwith other type of machines subjected to a fluid pressure drop duringmachine operation.

The machine 10 further includes a stator adaptor 25 coupled to thestator housing 14. In certain embodiments, the stator adaptor 25 extendsalong a circumferential direction 13 of the machine 10. In theillustrated embodiment, the stator adaptor 25 has an L-shaped profilehaving a projected end portion 27 extending towards the seal assembly16. The stator housing 14 extends along an axial direction 11 of themachine 10. The rotor 12 includes an extended portion 29 protrudingalong a radial direction 15 of the machine 10. In certain embodiments, arotatable seal component 18 and the rotor 12 are coupled to each othervia the extended portion 29. In some other embodiments, the rotatableseal component 18 and the rotor 12 are integrated to form a monolithiccomponent.

The seal assembly 16 includes a primary seal 21, a plurality of pairs ofbiasing members such as a plurality of pairs of flexures 22 disposedabout the axial direction 11, and a secondary seal 51. In someembodiments, the primary seal 21 includes the rotatable seal component18 and a non-rotatable seal component 20. The rotatable seal component18 is coupled to an end portion of the extended portion 29. Therotatable seal component 18 includes a rotor bearing face 24. In oneembodiment, the rotor bearing face 24 includes a plurality ofhydrodynamic elements (not shown in FIG. 1) disposed spaced apart fromeach other along the circumferential direction 13. The non-rotatableseal component 20 includes a stator bearing face 26 and a plurality ofisolated hydrostatic ports 31 (only two isolated hydrostatic port 31 areshown in FIG. 1) extending from a pressure cavity 33 to the statorbearing face 26. In the illustrated embodiment, the non-rotatable sealcomponent 20 has an L-shaped profile having a projected end portion 35extending away from the stator bearing face 26. In the illustratedembodiment, the machine 10 further includes a fluid supply tube 41having a first end coupled to a fluid source 43 and a second end coupledto the pressure cavity 33 via a tube connector 45. In the illustratedembodiment, the fluid source 43 is disposed outside the machine 10 andthe fluid supply tube 41 extends through the stator housing 14. In oneembodiment, the fluid source 43 may be a storage tank used for storing apressurized fluid 19. The fluid source 43 is further used to supply thepressurized fluid 19 to the pressure cavity 33 through the fluid supplytube 41. In one embodiment, the fluid supply tube 41 may be a flexiblepipe or a flexible conduit and the pressurized fluid 19 may be air. Insome other embodiments, the pressurized fluid 19 may be carbon dioxide,nitrogen, steam, and the like. In one embodiment, the machine 10 mayfurther include a pressure-control device coupled to the fluid supplytube 41. The pressure-control device may be a fluid pump used toincrease a pressure of the pressurized fluid 19 before supplying thepressurized fluid 19 to the pressure cavity 33 through the fluid supplytube 41.

The non-rotatable seal component 20 is coupled to the stator housing 14via the stator adaptor 25 and the plurality of pairs of flexures 22. Inone embodiment, each of the plurality of pairs of flexures 22 includes afirst flexure (not shown in FIG. 1) and a second flexure 66 disposed ina stressed condition such that a portion of the first flexure and aportion of the second flexure 66 are in contact with each other. In theillustrated embodiment, only the second flexure 66 is shown. A first endof the first flexure and a first end 32 a of the second flexure 66 arecoupled to each other and to the non-rotatable seal component 20 via afirst coupling member, for example, a grooved beam 30. Similarly, asecond end of the first flexure and a second end 32 b of the secondflexure 66 are coupled to each other and to the stator adaptor 25 via asecond coupling member, for example, a grooved flange 34. In certainembodiments, the plurality of pairs of flexures 22 is configured to movethe non-rotatable seal component 20 along the axial direction 11.Specifically, the plurality of pairs of flexures 22 is configured tolimit the movement of the non-rotatable seal component 20 along theradial direction 15.

The seal assembly 16 is disposed between the stator housing 14 and therotor 12 such that a clearance 36 (hereinafter also referred to as a“first clearance”) is established between the seal assembly 16 and therotor 12. Specifically, the non-rotatable seal component 20 is disposedfacing the rotatable seal component 18 such that the clearance 36 isdefined there between the stator bearing face 26 and the rotor bearingface 24. In certain embodiments, the rotatable seal component 18 and thenon-rotatable seal component 20 are used to regulate a flow of a portion(i.e., a first portion) of the process fluid 17 through the clearance36. In one embodiment, the illustrated portion of the machine 10 is anend packing area of a compressor. As used herein, the term “end packing”refers to a downstream end of the rotor 12, where the seal assembly 16is an interface between the rotor 12 and the stator housing 14.

The non-rotatable seal component 20 is slidably coupled to the statoradaptor 25 such that the projected end portion 35 of the non-rotatableseal component 20 slidably contacts the projected end portion 27 of thestator adaptor 25. The projected end portion 35 of the non-rotatableseal component 20 includes a recess 38 disposed facing the projected endportion 27 of the stator adaptor 25 such that a clearance 40(hereinafter also referred to as a “second clearance”) is definedtherebetween. In certain embodiments, the seal assembly 16 includes thesecondary seal 51 disposed in the recess 38 and configured to regulate aflow of a second portion of the process fluid 17 through the clearance40. In one embodiment, the secondary seal 51 is an O-ring. In certainembodiments, the secondary seal 51 is a C-shaped seal. In someembodiments, the process fluid 17 may be carbon dioxide. In theillustrated embodiment, the first flexure and the second flexure 66 areleaf springs.

During operation, the plurality of pairs of flexures 22 is configured tomove the seal assembly 16 along the axial direction 11. In one or moreembodiments, the stator bearing face 26 and the rotor bearing face 24may be in contact with each other during a stationary condition of themachine 10. The seal assembly 16 is used to regulate a leakage flow ofthe process fluid 17 from the regions “P₁,” “P₃” of relatively highpressure to the regions “P₂,” “P₄” of relatively low pressure. Theplurality of pairs of flexures 22 exerts either an opening force or aclosing force on the non-rotatable seal component 20 to move thenon-rotatable seal component 20 along a first axial direction 11 a or asecond axial direction 11 b opposite to the first axial direction 11 arelative to the rotatable seal component 18. Specifically, the sealassembly 16 generates the closing force by pushing the first end of thefirst flexure and the first end 32 a of the second flexure 66 andthereby moving the non-rotatable seal component 20 along the first axialdirection 11 a. Similarly, the seal assembly 16 generates the openingforce by pulling the first end of the first flexure and the first end 32a of the second flexure 66, and thereby retracting the non-rotatableseal component 20 along the second axial direction 11 b. Such a movementof the non-rotatable seal component 20 enables the seal assembly 16 totrack an axial movement of the rotor 12. Further, the first flexure andthe second flexure 66 of each of the plurality of pairs of flexures 22bias against each other to damp the vibrations or thermal expansion ofcomponents such as the non-rotatable seal component 20 and the statorhousing 14.

In some embodiments, the non-rotatable seal component 20 may be incontact with the rotatable seal component 18 at a zero-speed operatingcondition (i.e., stationary condition) of the machine 10. At thezero-speed operating condition, the rotor 12 may not generate enoughseparating force to move the stator bearing face 26 away from the rotorbearing face 24. As the speed of the rotor 12 increases, the pluralityof hydrodynamic elements generates an opening force to move the statorbearing face 26 away from the rotor bearing face 24 and a layer (i.e., athin-film) of the process fluid 17 is produced along the clearance 36.Then, the plurality of isolated hydrostatic ports 31 injects thepressurized fluid 19 against the rotor bearing face 24 to generate theseparating force (i.e., opening force) which is adequate to further movethe stator bearing face 26 away from the rotor bearing face 24 andproduce a relatively thick fluid-film of the process fluid 17 and thepressurized fluid 19 between the faces 24, 26. The thick-film regulatesa flow of the first portion of the process fluid 17 from the region “P₁”of high pressure to the region “P₂” of low pressure through theclearance 36. Further, the first flexure and the second flexure 66 ofeach of the plurality of pairs of flexures 22 maintain the clearance 36between the non-rotatable seal component 20 and the rotatable sealcomponent 18 by adjusting the opening and closing forces based on theaxial movement of the rotor 12. The first flexure and the second flexure66 of the plurality of pairs of flexures 22 bias against each otheralong the circumferential direction 13 to damp the vibrations or thermalexpansion of the components of the machine 10. The secondary seal 51regulates a flow of the second portion of the process fluid 17 from theregion “P₃” of high pressure to the region “P₄” of low pressure throughthe clearance 40.

In some other embodiments, at the zero-speed operating condition of themachine 10, the plurality of isolated hydrostatic ports 31 may be usedinitially to inject the pressurized fluid 19 to move the stator bearingface 26 away from the rotor bearing face 24. For example, at thezero-speed operating condition, the plurality of isolated hydrostaticports 31 injects the pressurized fluid 19 against the rotor bearing face24 to generate the separating force which is adequate to move the statorbearing face 26 away from the rotor bearing face 24. The pressurizedfluid 19 produces a thin-film along the clearance 36 between the rotorbearing face 24 and the stator bearing face 26. As a result, the faces24, 26 of the rotatable seal component 18 and non-rotatable sealcomponent 20 are prevented from rubbing against each other. When a speedof the rotor 12 is increased, the plurality of hydrodynamic elementsdisposed on the rotor bearing face 24 is further used to move the statorbearing face 26 away from the rotor bearing face 24 and produce arelatively thick fluid-film of the pressurized fluid 19 and the processfluid 17 between the faces 24, 26.

Conventionally, the stator seal component includes a tongue and adriving member has a groove to enable the tongue to slide along thegroove for moving the stator seal component along the axial direction.The groove may be clogged with dust particles over a period of use,thereby obstructing/limiting the axial movement of the stator sealcomponent. In accordance with the exemplary embodiment of FIG. 1, theseal assembly 16 does not have a groove and a tongue, thereby obviatingthe problems associated with dust accumulation discussed with referenceto the tongue and groove mechanism of a conventional seal assembly.Further, the use of leaf springs does not limit the axial movement ofthe non-rotatable seal component 20. Also, the first flexure and thesecond flexure 66 damps the generated vibrations and/or thermalexpansion of associated components.

FIG. 2 illustrates a perspective view of a portion of the rotor 12 ofFIG. 1, in accordance with one aspect of the present specification. Therotor 12 includes the extended portion 29 protruding along the radialdirection 15. The rotatable seal component 18 is coupled to an endportion of the extended portion 29. The rotatable seal component 18includes the rotor bearing face 24. In some embodiments, the rotorbearing face 24 includes a plurality of hydrodynamic elements 42disposed spaced apart from each other along the circumferentialdirection 13. In the illustrated embodiment, the plurality ofhydrodynamic elements 42 includes spiral grooves. In some otherembodiments, the plurality of hydrodynamic elements 42 may includeRayleigh steps or the like. In one or more embodiments, when the rotor12 is rotated, the plurality of hydrodynamic elements 42 produces afluid film (not shown) between the rotor bearing face 24 and the statorbearing face 26 (as shown in FIG. 1).

FIG. 3 illustrates a top view of a portion 62 of the seal assembly 16 ofFIG. 1, in accordance with one embodiment of the present specification.The portion 62 of the seal assembly 16 includes one pair of flexures 22,a plurality of first wedge washers 68, a plurality of second wedgewashers 69, and a plurality of fasteners 48. In certain embodiments, thepairs of flexures 22 includes the first flexure 64 and the secondflexure 66. In the illustrated embodiment, each of the first and secondflexures 64, 66 is a leaf spring. In one embodiment, the first flexure64 includes two shims 65 a, 65 b coupled to each other. Similarly, thesecond flexure 66 includes two shims 67 a, 67 b coupled to each other.

In one embodiment, each of the plurality of first and second wedgewashers 68, 69 has an inclined portion relative to a base portion. Forexample, a first wedge washer 68 a has an inclined portion 70 and a baseportion 72. The inclined portion 70 is inclined at a first angle “α₁”relative to the base portion 72. In one embodiment, the first angle “α₁”may be in a range from 20 degrees to 40 degrees. Similarly, a firstwedge washer 68 b has an inclined portion 71 and a base portion 73. Theinclined portion 71 is inclined at a second angle “α₂” relative to thebase portion 73. In one embodiment, the second angle “α₂” may be in arange from 130 degrees to 150 degrees. Further, a second wedge washer 69a has an inclined portion 74 and a base portion 76. The inclined portion74 is inclined at a third angle “α₃” relative to the base portion 76. Inone embodiment, the third angle “α₃” may be in a range from 310 degreesto 340 degrees. Similarly, a second wedge washer 69 b has an inclinedportion 75 and a base portion 77. The inclined portion 75 is inclined ata fourth angle “α₄” relative to the base portion 77. In one embodiment,the fourth angle “α₄” may be in a range from 210 degrees to 240 degrees.

In the illustrated embodiment, the first and second wedge washers 68 a,69 a are disposed proximate to first ends 28 a, 32 a of the first andsecond flexures 64, 66 respectively. Similarly, the first and secondwedge washers 68 b, 69 b are disposed proximate to second ends 28 b, 32b of the first and second flexures 64, 66 respectively. In theillustrated embodiment, the base portion 72 of the first wedge washer 68a contacts the base portion 76 of the second wedge washer 69 a.Similarly, the base portion 73 of the first wedge washer 68 b contactsthe base portion 77 of the second wedge washer 69 b. Further, the firstand second flexures 64, 66 are coupled to each other and to thenon-rotatable seal component 20 (shown in FIG. 1). The first ends 28 a,32 a of the first and second flexures 64, 66 are coupled to each othervia a fastener of the plurality of fasteners 48 and to the non-rotatableseal component 20 via the grooved beam 30 (shown in FIG. 1). In theillustrated embodiment, each fastener of the plurality of fasteners 48extends through a hole (not labeled) formed in the first ends 28 a, 32 aof the first and second flexures 64, 66 and through a hole (not labeled)formed in the first and second wedge washers 68 a, 69 a. Similarly, thefirst and second flexures 64, 66 are further coupled to each other andto a stator housing 14 via the stator adaptor 25 (shown in FIG. 1). Thesecond ends 28 b, 32 b of the first and second flexures 64, 66 arecoupled to each other via a fastener of the plurality of fasteners 48and to the stator adaptor 25 via the grooved flange 34 (shown in FIG.1). In the illustrated embodiment, each fastener of the plurality offasteners 48 extends through a hole (not labeled) formed in the secondends 28 b, 32 b of the first and second flexures 64, 66 and through ahole (not labeled) formed in the first and second wedge washers 68 b, 69b.

Each of the first and second flexures 64, 66 is disposed in a stressedcondition such that a portion 78, for example, a central portion of thefirst flexure 64 contacts a portion 56, for example, a central portionof the second flexure 66. In one embodiment, a first end portion 64 a ofthe first flexure 64 is inclined at a first angle “β₁” relative to thebase portion 72 of the first wedge washer 68 a. A second end portion 64b of the first flexure 64 is inclined at a second angle “β₂” relative tothe base portion 73 of the first wedge washer 68 b. A first end portion66 a of the second flexure 66 is inclined at a third angle “β₃” relativeto the base portion 76 of the second wedge washer 69 a. A second endportion 66 b of the second flexure 66 is inclined at a fourth angle “β₄”relative to the base portion 77 of the second wedge washer 69 b.

The first and second flexures 64, 66 are disposed in a stressedcondition to increase the natural frequency and stiffness along theradial direction. Stiffness of the first and second flexures 64, 66 arereduced along the axial direction. The stressed condition of the firstand second flexures 64, 66 further enables the pairs of flexures 22 tomove the non-rotatable seal component along the axial direction of themachine. Further, the first and second flexures 64, 66 are used to dampthe vibrations of the non-rotatable seal component and the statorhousing.

In some embodiments, the plurality of first wedge washers 68 and thefirst flexure 64 are integrated to each other to form a first monolithiccomponent. Similarly, the plurality of second wedge washers 69 and thesecond flexure 66 are integrated to each other to form a secondmonolithic component. The first and second monolithic components may bemanufactured using additive manufacturing techniques.

In the illustrated embodiment, the portions 78, 56 of the first andsecond flexures 64, 66 are provided with wear resistant coatings 61, 63respectively. In one embodiment, the portions 78, 56 correspond to thecentral portions of the first and second flexures 64, 66 respectively.

FIG. 4 illustrates a side view of one third flexure 82, in accordancewith one embodiment of the present specification. In the illustratedembodiment, the third flexure 82 is a leaf spring. In one embodiment,the leaf spring may include a plurality of shims coupled to each other.A first end 84 of the third flexure 82 may be coupled to thenon-rotatable seal component of the seal assembly and a second end 86 ofthe third flexure 82 may be coupled to the stator housing of themachine. The third flexure 82 further includes a plurality ofthrough-holes 88 formed at the first end 84 and the second end 86. Theplurality of through-holes 88 may be used for inserting the fastener ofthe plurality of fasteners to fasten the third flexure 82 to the firstand second flexures.

In the illustrated embodiment, the third flexure 82 has a truss-likestructure 90 having a plurality of through-openings 92 extending from afirst peripheral surface 94 to a second peripheral surface 96. Theplurality of through-openings 92 may be spaced apart from each otheralong a longitudinal direction “L” of the third flexure 82. Thetruss-like structure 90 enables regulation of an axial stiffness of thethird flexure 82. Further, the truss-like structure 90 enablesmaximization of a stiffness of the non-rotatable seal component along aradial direction of the machine relative to the stiffness of thenon-rotatable seal component along an axial direction of the machine.The third flexure 82 further includes a wear resistant coating 98disposed on a portion (e.g. central portion) of the first peripheralsurface 94 and a wear resistant coating 100 (shown in FIG. 5) disposedon a portion (e.g. a central portion) of the second peripheral surface96.

Although not illustrated, the first and second flexures 64, 66 may alsohave a truss-like structure 90 as discussed herein with respect toembodiment of FIG. 4. Specifically, the truss-like structure 90maximizes the stiffness of the non-rotatable seal component along theradial direction of the machine relative to the stiffness of thenon-rotatable seal component along the axial direction of the machine.

FIG. 5 illustrates a top view of a portion 162 of a seal assembly 116,in accordance with another embodiment of the present specification. Theseal assembly 116 includes a pair of flexures 123, at least one thirdflexure 83, a plurality of first wedge washers 168, a plurality ofsecond wedge washers 169, and a plurality of fasteners 148. The pair offlexures 123 includes a first flexure 164 and a second flexure 166. Inthe illustrated embodiment, each of the first flexure 164, the secondflexure 166, and the at least one third flexure 83 is a leaf spring. Insome other embodiments, the number of flexures may vary depending on theapplication and design criteria.

In the illustrated embodiment, the at least one third flexure 83 isdisposed between the first and second flexures 164, 166. The pluralityof first wedge washers 168 is disposed between the first flexure 164 andthe at least one third flexure 83. The plurality of second wedge washers169 is disposed between the second flexure 166 and the at least onethird flexure 83. The plurality of first wedge washers 168 is disposedproximate to a first end 85 and a second end 87 of the at least onethird flexure 83. The first flexure 164 includes a first end 128 adisposed proximate to the first end 85 of the at least one third flexure83 and a second end 128 b disposed proximate to the second end 87 of theat least one third flexure 83. The second flexure 166 includes a firstend 132 a disposed proximate to the first end 85 of the at least onethird flexure 83 and a second end 132 b disposed proximate to the secondend 87 of the at least one third flexure 83. The first ends 128 a, 132 aare coupled to each other via a fastener of the plurality of fasteners148 extending through the plurality of first and second wedge washers168, 169, the first and second flexures 164, 166, and the at least onethird flexure 83. Similarly, the second ends 128 b, 132 b are coupled toeach other via a fastener of the plurality of fasteners 148 extendingthrough the plurality of first and second wedge washers 168, 169, thefirst and second flexures 164, 166, and the at least one third flexure83. The first ends 128 a, 132 a are further coupled to the non-rotatableseal component and the second ends 128 b, 132 b are coupled to thestator housing.

In the illustrated embodiment, a first wedge washer 168 a of theplurality of first wedge washers 168 has an inclined portion 170 and abase portion 172. The inclined portion 170 is inclined at a first angle“α₁” relative to the base portion 172. In one embodiment, the firstangle “α₁” may be in a range from 20 degrees to 40 degrees. Similarly, afirst wedge washer 168 b of the plurality of first wedge washers 168 hasan inclined portion 171 and a base portion 173. The inclined portion 171is inclined at a second angle “α₂” relative to the base portion 173. Inone embodiment, the second angle “α₂” may be in a range from 130 degreesto 150 degrees. A second wedge washer 169 a of the plurality of secondwedge washers 169 has an inclined portion 174 and a base portion 176.The inclined portion 174 is inclined at a third angle “α₃” relative tothe base portion 176. In one embodiment, the third angle “α₃” may be ina range from 310 degrees to 340 degrees. Similarly, a second wedgewasher 169 b of the plurality of second wedge washers 169 has aninclined portion 175 and a base portion 177. The inclined portion 175 isinclined at a fourth angle “α₄” relative to the base portion 177. In oneembodiment, the fourth angle “α₄” may be in a range from 210 degrees to240 degrees. In the illustrated embodiment, the first wedge washers 168a, 168 b are disposed proximate to the first end 85 of the at least onethird flexure 83 and the second wedge washers 168 b, 169 b are disposedproximate to the second end 87 of the at least one third flexure 83.

In one embodiment, the first flexure 164 is disposed in a stressedcondition such that a portion, for example, a central portion of aperipheral surface 178 of the first flexure 164 contacts a portion, forexample, a central portion of a first peripheral surface 95 of the atleast one third flexure 83. A first end portion 164 a of the firstflexure 164 is inclined at a first angle “β₁” relative to the firstperipheral surface 95 of the at least one third flexure 83. A second endportion 164 b of the first flexure 164 is inclined at a second angle“β₂” relative to the first peripheral surface 95 of the at least onethird flexure 83.

The second flexure 166 is disposed in a stressed condition such that aportion, for example, a central portion of a peripheral surface 180 ofthe second flexure 166 contacts a portion, for example, a centralportion of the second peripheral surface 97 of the at least one thirdflexure 83. In one embodiment, a first end portion 166 a of the secondflexure 166 is inclined at a third angle “β₃” relative to the secondperipheral surface 97 of the at least one third flexure 83. A second endportion 166 b of the second flexure 166 is inclined at a fourth angle“β₄” relative to the second peripheral surface 97 of the at least onethird flexure 83.

The first and second flexures 164, 166 are disposed in the stressedcondition to increase a natural frequency and stiffness along a radialdirection, thereby decreasing the stiffness along an axial direction.Stacking of the first and second flexures 164, 166 in a stressedcondition against the at least one third flexure 83 results inpreloading the first and second flexures 164, 166 in a natural vibrationmode. As a result, stiffness of the seal assembly 116 is increased alongthe radial direction (i.e., natural vibration mode) and stiffness of theseal assembly 116 is decreased along the axial direction. The first andsecond flexures 164, 166 enable the damping of the vibrations of thenon-rotatable seal component and the stator housing. Portions, forexample, the central portions of the first and second flexures 164, 166are provided with wear resistant coatings 161, 163 respectively.Similarly, the portion, e.g. central portion of the first peripheralsurface 95 of the at least one third flexure 83 and the portion, e.g.central portion of the second peripheral surface 97 of the at least onethird flexure 83 are provided with wear resistant coatings 98 a, 98 brespectively. The portion of the first flexure 164 rubs against theportion of the first peripheral surface 95 of the at least one thirdflexure 83 and the portion of the second flexure 166 rubs against theportion of the second peripheral surface 97 of the at least one thirdflexure 83, resulting in dissipation of heat from the non-rotatable sealcomponent to the stator housing.

FIG. 6 is a top view of a portion 262 of a seal assembly 216, inaccordance with yet another embodiment of the present specification. Inone embodiment, the seal assembly 216 includes a pair of flexures 223, aplurality of third flexures 282, a plurality of first wedge washers 268,a plurality of second wedge washers 269, and a plurality of fasteners248. The pair of flexures 223 includes a first flexure 264 and a secondflexure 266. In the illustrated embodiment, each of the first and secondflexures 264, 266 is a leaf spring and each of the plurality of thirdflexures 282 is a W-shaped spring. First ends 228 a, 232 a of the firstflexure 264 and the second flexure 266 respectively are coupled to eachother via a fastener of the plurality of fasteners 248 extending throughthe plurality of first and second wedge washers 268, 269 and through thefirst and second flexures 264, 266. Similarly, second ends 228 b, 232 bof the first flexure 264 and the second flexure 266 respectively arecoupled to each other via a fastener of the plurality of fasteners 248extending through the plurality of first and second wedge washers 268,269 and through the first and second flexures 264, 266. The first ends228 a, 232 a are further coupled to the non-rotatable seal component andthe second ends 228 b, 232 b are coupled to the stator housing.

In the illustrated embodiment, the plurality of third flexures 282 isdisposed between the first and second flexures 264, 266. The first andsecond flexures 264, 266 are disposed in a stressed condition such thata portion of each of the first and second flexures 264, 266 are incontact with each other via the plurality of third flexures 282. In theillustrated embodiment, a first end 284 of one third flexure 282 a iscoupled to the first flexure 264 and a second end 286 of the thirdflexure 282 a is coupled to a bump or an enclosure 288 coupled to thesecond flexure 266. The seal assembly 216 is used to damp vibrations ofthe non-rotatable seal component and the stator housing by biasing thefirst and second flexures 264, 266 against each other via the pluralityof third flexures 282.

FIG. 7 is a top view of a portion 362 of a seal assembly 316, inaccordance with yet another embodiment of the present specification. Theseal assembly 316 includes a pair of flexures 323, a plurality of thirdflexures 382, a plurality of first wedge washers 368, a plurality ofsecond wedge washers 369, and a plurality of fasteners 348. The pair offlexures 323 includes a first flexure 364 and a second flexure 366. Inthe illustrated embodiment, each of the first and second flexures 364,366 is a leaf spring and each of the plurality of third flexures 382 isa V-shaped spring. Moreover, in the illustrated embodiment, theplurality of third flexures 382 is disposed between the first and secondflexures 364, 366. The first and second flexures 364, 366 are disposedin a stressed condition such that a portion of each of the first andsecond flexures 364, 366 are in contact with each other via theplurality of third flexures 382. In the illustrated embodiment, a firstend 384 of one third flexure 382 a is coupled to the first flexure 364and a second end 386 of the one third flexure 382 a is coupled to a bumpor an enclosure 388 coupled to the second flexure 366. The seal assembly316 is used to damp vibrations of the non-rotatable seal component andthe stator housing by biasing the first and second flexures 364, 366against each other via the plurality of third flexures 382.

FIG. 8 is a top view of a portion 462 of a seal assembly 416 inaccordance with yet another embodiment of the present specification. Theseal assembly 416 includes a pair of flexures 423, a plurality of thirdflexures 482, a plurality of first wedge washers 468, a plurality ofsecond wedge washers 469, and a plurality of fasteners 448. The pair offlexures 423 includes a first flexure 464 and a second flexure 466. Inthe illustrated embodiment, each of the first and second flexures 464,466 is a leaf spring and each of the plurality of third flexures 482 isa bellow spring. In the illustrated embodiment, the plurality of thirdflexures 482 is disposed between the first and second flexures 464, 466.The first and second flexures 464, 466 are disposed in a stressedcondition such that a portion of each of the first and second flexures464, 466 are in contact with each other via the plurality of thirdflexures 482. In the illustrated embodiment, a first end 484 of onethird flexure 482 a is coupled to the first flexure 464 and a second end486 of the one third flexure 482 a is coupled to a bump or an enclosure488 coupled to the second flexure 466. The seal assembly 416 is used todamp vibrations of the non-rotatable seal component and the statorhousing by biasing the first and second flexures 464, 466 against eachother via the plurality of third flexures 482.

FIG. 9 is a flow chart illustrating a method 500 of operating a sealassembly, in accordance with aspects of the present specification. Inone embodiment, the method 500 includes a step 502 of driving arotatable seal component coupled to a rotor disposed inside a statorhousing. In some embodiments, the rotation of the rotor may cause aplurality of hydrodynamic elements formed in a rotor bearing face of therotatable seal component to form a thin film of a process fluid along aclearance defined between the non-rotatable seal component and therotatable seal component. Further, the method 500 includes a step 504 ofinjecting a pressurized fluid via a non-rotatable seal component againstthe rotatable seal component and forming a layer (i.e., a thick film) ofthe pressurized fluid and the process fluid along the clearance. In someembodiments, steps 502 and 504 are performed sequentially. In some otherembodiments, steps 502 and 504 are performed simultaneously. In oneembodiment, the step 504 of injecting the pressurized fluid may beperformed before the step 502 of driving a rotatable seal component.

The method 500 further includes a step 506 of regulating a flow of aportion of the process fluid through the clearance by the film. Themethod 500 further includes a step 508 of moving the non-rotatable sealcomponent along an axial direction relative to the rotatable sealcomponent, using a plurality of pairs of flexures. In some embodiments,the plurality of pairs of flexures exerts either an opening force or aclosing force on the non-rotatable seal component to move thenon-rotatable seal component along a first axial direction or a secondaxial direction opposite to the first axial direction relative to therotatable seal component. The method further includes a step 510 ofadjusting a movement of the non-rotatable seal component, using theplurality of pairs of flexures to maintain the clearance between thenon-rotatable seal component the rotatable seal component. Such amovement of the non-rotatable seal component enables the seal assemblyto track an axial movement of the rotor such that the non-rotatable sealcomponent does not contact the rotatable seal component. Further, themethod 500 includes a step 512 of damping vibrations of thenon-rotatable seal component and the stator housing by biasing a firstflexure and a second flexure of each pair of the plurality of pairs offlexures against each other. In one embodiment, at least one flexure ofthe first flexure, the second flexure, and the at least one thirdflexure is a leaf spring. In another embodiment, one flexure of theplurality of third flexures is at least one of a bellow spring, aW-shaped spring, and a V-shaped spring.

In accordance with certain embodiments discussed herein, the exemplarydamped biasing member (a plurality of pairs of flexures and/or at leastone third flexure) for a seal assembly provides a large span for anaxial motion of a non-rotatable seal component while limiting a radialmotion of the non-rotatable seal component. Further, the damped biasingmember aids in attenuating vibrations generated by a machine. Inaddition, the plurality of pairs of flexures and/or the at least onethird flexure enable heat dissipation from the seal assembly.

While only certain features of embodiments have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedembodiments are intended to cover all such modifications and changes asfalling within the spirit of the disclosed technique.

The invention claimed is:
 1. A seal assembly comprising: a rotatableseal component; a non-rotatable seal component disposed facing therotatable seal component; a plurality of pairs of flexures spaced apartfrom each other along a circumferential direction of the seal assembly,wherein each pair of the plurality of pairs of flexures comprises afirst flexure and a second flexure disposed in a stressed condition suchthat a portion of the first flexure and a portion of the second flexureare in contact with each other, and wherein an end of the first flexureand an end of the second flexure are coupled to each other and to thenon-rotatable seal component; a plurality of third flexures, wherein atleast one third flexure of the plurality of third flexures is disposedbetween the first and second flexures; a plurality of first wedgewashers; a plurality of second wedge washers; and a plurality offasteners, wherein the plurality of first wedge washers is disposedbetween the first flexure and the at least one third flexure, whereinthe plurality of second wedge washers is disposed between the secondflexure and the at least one third flexure, and wherein the firstflexure and the second flexure are coupled to each other via theplurality of fasteners extending through the plurality of first andsecond wedge washers and the at least one third flexure.
 2. The sealassembly of claim 1, wherein the plurality of first wedge washers andthe first flexure are integrated with each other, and wherein theplurality of second wedge washers and the second flexure are integratedwith each other.
 3. The seal assembly of claim 1, wherein the portion ofthe first flexure contacts a portion of a first peripheral surface ofthe at least one third flexure and the portion of the second flexurecontacts a portion of a second peripheral surface of the at least onethird flexure.
 4. The seal assembly of claim 3, wherein at least one ofthe portion of the first peripheral surface and the portion of thesecond peripheral surface comprises a wear resistant coating.
 5. Theseal assembly of claim 3, wherein at least one of the portion of thefirst flexure and the portion of the second flexure comprises a wearresistant coating.
 6. The seal assembly of claim 3, wherein at least oneof the first and second flexures and the at least one third flexurecomprises a leaf spring.
 7. The seal assembly of claim 6, wherein theleaf spring comprises one or more shims that are in contact with eachother.
 8. The seal assembly of claim 6, wherein at least one of thefirst and second flexures and the at least one third flexure comprises atruss-like structure.
 9. The seal assembly of claim 1, wherein the atleast one third flexure comprises a first end and a second end, andwherein one of the first and second ends is coupled to the first orsecond flexure.
 10. The seal assembly of claim 9, wherein at least oneof the first and second flexures comprises a leaf spring, and whereinthe at least one third flexure comprises at least one of a bellowspring, a W-shaped spring, and a V-shaped spring.
 11. A machinecomprising: a stator housing; a rotor disposed in the stator housing; aseal assembly disposed between the stator housing and the rotor, whereinthe seal assembly comprises: a rotatable seal component coupled to therotor; a non-rotatable seal component disposed facing the rotatable sealcomponent; a plurality of pairs of flexures disposed spaced apart fromeach other along a circumferential direction of the seal assembly,wherein each pair of the plurality of pairs of flexures comprises afirst flexure and a second flexure disposed in a stressed condition suchthat a portion of the first flexure and a portion of the second flexureare in contact with each other, wherein a first end of the first flexureand a first end of the second flexure are coupled to each other and tothe non-rotatable seal component, and wherein a second end of the firstflexure and a second end of the second flexure are coupled to each otherand to the stator housing; a plurality of third flexures, wherein atleast one third flexure of the plurality of third flexures is disposedbetween the first and second flexures; a plurality of first wedgewashers; a plurality of second wedge washers; and a plurality offasteners, wherein the plurality of first wedge washers is disposedbetween the first flexure and the at least one third flexure, whereinthe plurality of second wedge washers is disposed between the secondflexure and the at least one third flexure, and wherein the firstflexure and the second flexure are coupled to each other via theplurality of fasteners extending through the plurality of first andsecond wedge washers and the at least one third flexure.
 12. The machineof claim 11, wherein the plurality of first wedge washers and the firstflexure are integrated with each other, and wherein the plurality ofsecond wedge washers and the second flexure are integrated with eachother.
 13. The machine of claim 12, wherein the portion of the firstflexure contacts a portion of a first peripheral surface of the at leastone third flexure and the portion of the second flexure contacts aportion of a second peripheral surface of the at least one thirdflexure.
 14. The machine of claim 13, wherein at least one of theportion of the first peripheral surface and the portion of the secondperipheral surface comprises a wear resistant coating, and wherein atleast one of the portion of the first flexure and the portion of thesecond flexure comprises a wear resistant coating.
 15. The machine ofclaim 14, wherein at least one of first and second flexures, and the atleast one third flexure comprises a truss-like structure.
 16. Themachine of claim 11, wherein the at least one third flexure comprises afirst end and a second end, and wherein one of the first and second endsis coupled to the first or second flexure.
 17. The machine of claim 16,wherein at least one of the first and second flexures comprises a leafspring comprising a plurality of shims that contact each other, andwherein the at least one third flexure comprises at least one of abellow spring, a W-shaped spring, and a V-shaped spring.
 18. A methodcomprising: driving a rotatable seal component coupled to a rotordisposed inside a stator housing; injecting a pressurized fluid via anon-rotatable seal component against the rotatable seal component andforming a layer of the pressurized fluid and a process fluid in aclearance defined between the rotatable seal component and thenon-rotatable seal component; regulating a flow of a portion of theprocess fluid through the clearance; moving the non-rotatable sealcomponent along an axial direction relative to the rotatable sealcomponent, using a plurality of pairs of flexures, wherein each pair ofthe plurality of pairs of flexures comprises a first flexure and asecond flexure disposed in a stressed condition such that a portion ofthe first flexure and a portion of the second flexure are in contactwith each other, and wherein a first end of the first flexure and afirst end of the second flexure are coupled to each other and to thenon-rotatable seal component, and a second end of the first flexure anda second end of the second flexure are coupled to each other and to thestator housing; adjusting movement of the non-rotatable seal component,using the plurality of pairs of flexures and the layer of thepressurized fluid and the process fluid to maintain the clearancebetween the non-rotatable seal component and the rotatable sealcomponent; and damping vibrations of the non-rotatable seal componentand the stator housing by biasing the first flexure and the secondflexure against each other.
 19. The method of claim 18, wherein dampingvibrations of the non-rotatable seal component and the stator housingfurther comprises biasing the first and second flexures against at leastone third flexure of a plurality of third flexures, and wherein the atleast one third flexure of the plurality of third flexures is disposedbetween the first and second flexures.
 20. The method of claim 19,further comprising dissipating heat from the non-rotatable sealcomponent due to rubbing the portion of the first flexure against aportion of a first peripheral surface of the at least one third flexureand the portion of the second flexure against a portion of a secondperipheral surface of the at least one third flexure.